Coated cutting tool

ABSTRACT

A coated cutting tool comprising a substrate and a coating layer formed on a surface of the substrate, the coating layer including at least one α-type aluminum oxide layer, wherein, in the α-type aluminum oxide layer, a texture coefficient TC (1,2,11) of a (1,2,11) plane is 1.4 or more. 
     
       
         
           
             
               
                 
                   
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     (In formula (1), I (h,k,l) denotes a peak intensity for an (h,k,l) plane in X-ray diffraction of the α-type aluminum oxide layer, I 0  (h,k,l) denotes a standard diffraction intensity for an (h,k,l) plane which is indicated on a JCPDS Card No. 10-0173 for α-type aluminum oxide, and (h,k,l) refers to eight crystal planes of (0,1,2), (1,0,4), (1,1,0), (1,1,3), (0,2,4), (1,1,6), (2,1,4) and (1,2,11).)

TECHNICAL FIELD

The present invention relates to a coated cutting tool.

BACKGROUND ART

It has been conventionally well known to employ, for the cutting ofsteel, cast iron, etc., a coated cutting tool which is obtained bydepositing, via chemical vapor deposition, a coating layer with a totalthickness of from 3 μm or more to 20 μm or less on a surface of asubstrate consisting of a cemented carbide. A known example of the abovecoating layer is a coating layer consisting of a single layer of onekind selected from the group consisting of a Ti carbide, a Ti nitride, aTi carbonitride, a Ti carbonate, a Ti carboxynitride, and aluminumoxide, or consisting of multiple layers of two or more kinds selectedtherefrom.

As to techniques for improving the fracture resistance of a coatedcutting tool, JPH09-507528 T discloses that wear and toughnessproperties are enhanced by controlling the particle size and thicknessof an aluminum oxide layer and also by setting a texture coefficient ofa (104) plane so as to be greater than 1.5.

JP5902865 B discloses a coating tool in which at least a titaniumcarbonitride layer and an aluminum oxide layer having an α-typecrystalline structure are located, on a substrate surface, in order fromthe substrate side, wherein, in X-ray diffraction analysis of analuminum oxide layer, with regard to a texture coefficient (116)represented by Tc (hkl) of the aluminum oxide layer, a surface-side Tc(116) in a surface-side peak is greater than a substrate-side Tc (116)in a substrate-side peak, where the substrate side Tc (116) is from 0.3or more to 0.7 or less.

SUMMARY Technical Problem

An increase in speed, feed and depth of cut have become more conspicuousin cutting in recent times, and the fracture resistance of a tool isrequired to be further improved compared to that involved in the priorart. In particular, in recent times, there has been a growth in cuttingin which the cutting temperature is high, such as high-speed cutting ofsteel, and under such severe cutting conditions, a conventional cuttingtool is likely to involve the progress of chemical reaction wear of acoating layer thereof. This triggers a problem in that the occurrence ofcrater wear and the insufficient strength of the edge result infracturing, which does not allow the tool life to be extended.

Based on such background, when only the crystal orientation of an α-typealuminum oxide layer is controlled to achieve preferential orientationof a (104) plane or a (116) plane, as in the tools disclosed in PatentDocuments 1 and 2 above, sufficient fracture resistance cannot beachieved under cutting conditions which place a large load on a coatedcutting tool.

The present invention has been made in order to solve this problem, andan object of the present invention is to provide a coated cutting toolwhich has excellent wear resistance and fracture resistance and therebyallows the tool life to be extended.

Solution to Problem

The present inventor has conducted studies regarding extending the toollife of a coated cutting tool from the above-described perspective andhas then found that the following configurations, including optimizingthe crystal orientation in a predetermined plane of an α-type aluminumoxide layer, allow the wear resistance to be improved as the progress ofchemical reaction wear is suppressed, and also allow the fractureresistance to be improved, and found that, as a result, the tool life ofthe coated cutting tool can be extended, and this has led to thecompletion of the present invention.

Namely, the present invention is as set forth below:

(1) A coated cutting tool comprising a substrate and a coating layerformed on a surface of the substrate, the coating layer including atleast one α-type aluminum oxide layer, wherein, in the α-type aluminumoxide layer, a texture coefficient TC (1,2,11) of a (1,2,11) planerepresented by formula (1) below is 1.4 or more.

$\begin{matrix}{{{TC}\left( {1,2,11} \right)} = {\frac{I\left( {1,2,11} \right)}{I_{0}\left( {1,2,11} \right)}\left\{ {\frac{1}{8}{\sum\frac{I\left( {h,k,l} \right)}{I_{0}\left( {h,k,l} \right)}}} \right\}^{- 1}}} & (1)\end{matrix}$(In formula (1), I (h,k,l) denotes a peak intensity for an (h,k,l) planein X-ray diffraction of the α-type aluminum oxide layer, I₀ (h,k,l)denotes a standard diffraction intensity for an (h,k,l) plane which isindicated on a JCPDS Card No. 10-0173 for α-type aluminum oxide, and(h,k,l) refers to eight crystal planes of (0,1,2), (1,0,4), (1,1,0),(1,1,3), (0,2,4), (1,1,6), (2,1,4) and (1,2,11).)

(2) The coated cutting tool of (1), wherein, in the α-type aluminumoxide layer, the texture coefficient TC (1,2,11) is from 2.0 or more to6.9 or less.

(3) The coated cutting tool of (1) or (2), wherein a residual stressvalue in a (1,1,6) plane of the α-type aluminum oxide layer is, in atleast part thereof, from −300 MPa or higher to 300 MPa or lower.

(4) The coated cutting tool of any one of (1) to (3), wherein an averagethickness of the α-type aluminum oxide layer is from 1.0 μm or more to15.0 μm or less.

(5) The coated cutting tool of any one of (1) to (4), wherein thecoating layer comprises a TiCN layer between the substrate and theα-type aluminum oxide layer, and a ratio I₃₁₁/I₂₂₀ of a peak intensityI₃₁₁ for a (3,1,1) plane in X-ray diffraction of the TiCN layer to apeak intensity I₂₂₀ for a (2,2,0) plane in X-ray diffraction of the TiCNlayer is from 1.5 or more to 20.0 or less.

(6) The coated cutting tool of (5), wherein the coating layer comprises,between the TiCN layer and the α-type aluminum oxide layer, anintermediate layer comprised of a compound of at least one kind selectedfrom the group consisting of a Ti carbonate, a Ti oxynitride and a Ticarboxynitride.

(7) The coated cutting tool of (5) or (6), wherein an average thicknessof the TiCN layer is from 2.0 μm or more to 20.0 μm or less.

(8) The coated cutting tool of any one of (1) to (7), wherein an averagethickness of the coating layer is from 3.0 μm or more to 30.0 μm orless.

(9) The coated cutting tool of any one of (1) to (8), wherein thecoating layer comprises a TiN layer as an outermost layer on a sideopposite to the substrate.

(10) The coated cutting tool of any one of (1) to (9), wherein thesubstrate is comprised of any of a cemented carbide, cermet, ceramicsand a sintered body containing cubic boron nitride.

The present invention can provide a coated cutting tool which hasexcellent wear resistance and fracture resistance and thereby allows thetool life to be extended.

DESCRIPTION OF EMBODIMENTS

An embodiment for carrying out the present invention (hereinafter simplyreferred to as the “present embodiment”) will hereinafter be describedin detail. However, the present invention is not limited to the presentembodiment below. Various modifications may be made to the presentinvention without departing from the gist of the invention.

A coated cutting tool according to the present embodiment comprises asubstrate and a coating layer formed on a surface of the substrate.Specific examples of types of the coated cutting tool include anindexable cutting insert for milling or turning, a drill and an endmill.

The substrate in the present embodiment is not particularly limited, aslong as it may be used as a substrate for the coated cutting tool.Examples of such substrate include a cemented carbide, cermet, ceramic,a sintered body containing cubic boron nitride, a diamond sintered bodyand high-speed steel. From among the above examples, the substrate ispreferably comprised of any of a cemented carbide, cermet, ceramics anda sintered body containing cubic boron nitride, as this providesexcellent wear resistance and fracture resistance, and, from the sameperspective, the substrate is more preferably comprised of a cementedcarbide.

It should be noted that the surface of the substrate may be modified.For instance, when the substrate is comprised of a cemented carbide, aβ-free layer may be formed on the surface thereof, and when thesubstrate is comprised of cermet, a hardened layer may be formed on thesurface thereof. The operation and effects of the present invention arestill provided, even if the substrate surface has been modified in thisway.

As to the coating layer in the present embodiment, the average thicknessthereof is preferably from 3.0 μm or more to 30.0 μm or less. If theaverage thickness is 3.0 μm or more, this indicates the tendency of thewear resistance to be further improved, and if such average thickness is30.0 μm or less, this indicates the tendency of the adhesion with thesubstrate of the coating layer and the fracture resistance to be furtherincreased. From the same perspective, the average thickness of thecoating layer is more preferably from 5.0 μm or more to 27.0 μm or less.It should be noted that, as to the average thickness of each layer andthe average thickness of the entire coating layer in the coated cuttingtool of the present embodiment, each of such average thicknesses can beobtained by: measuring the thickness of each layer or the thickness ofthe entire coating layer from each of the cross-sectional surfaces atthree or more locations in each layer or in the entire coating layer;and calculating the arithmetic mean of the resulting measurements.

The coating layer in the present embodiment includes at least one α-typealuminum oxide layer. In the α-type aluminum oxide layer, a texturecoefficient TC (1,2,11) of a (1,2,11) plane represented by formula (1)below is 1.4 or more. When the texture coefficient TC (1,2,11) is 1.4 ormore, the ratio of a peak intensity I (1,2,11) for the (1,2,11) plane ishigh, resulting in excellent wear resistance because chemical reactionwear can be suppressed. From the same perspective, the texturecoefficient TC (1,2,11) in the α-type aluminum oxide layer is preferably1.5 or more, is more preferably 2.0 or more, is further preferably 3.0or more, and is particularly preferably 4.0 or more. Further, thetexture coefficient TC (1,2,11) is preferably 6.9 or less.

$\begin{matrix}{{{TC}\left( {1,2,11} \right)} = {\frac{I\left( {1,2,11} \right)}{I_{0}\left( {1,2,11} \right)}\left\{ {\frac{1}{8}{\sum\frac{I\left( {h,k,l} \right)}{I_{0}\left( {h,k,l} \right)}}} \right\}^{- 1}}} & (1)\end{matrix}$

Herein, in formula (1), I (h,k,l) denotes a peak intensity for an(h,k,l) plane in X-ray diffraction of the α-type aluminum oxide layer,I₀ (h,k,l) denotes a standard diffraction intensity for the (h,k,l)plane which is indicated on a JCPDS Card No. 10-0173 for α-type aluminumoxide, and (h,k,l) refers to eight crystal planes of (0,1,2), (1,0,4),(1,1,0), (1,1,3), (0,2,4), (1,1,6), (2,1,4) and (1,2,11). Accordingly, I(1,2,11) denotes a peak intensity for the (1,2,11) plane in X-raydiffraction of the α-type aluminum oxide layer, and I₀ (1,2,11) denotesa standard diffraction intensity for the (1,2,11) plane which isindicated on a JCPDS Card No. 10-0173 for α-type aluminum oxide. Itshould be noted that the standard diffraction intensities for therespective crystal planes are 75.0 for a (0,1,2) plane, 90.0 for a(1,0,4) plane, 40.0 for a (1,1,0) plane, 100.0 for a (1,1,3) plane, 45.0for a (0,2,4) plane, 80.0 for a (1,1,6) plane, 30.0 for a (2,1,4) planeand 1.0 for a (1,2,11) plane. In the present embodiment, if the texturecoefficient TC (1,2,11) is 1.4 or more, this indicates the tendency ofthe α-type aluminum oxide layer to have preferential orientation of the(1,2,11) plane. In particular, if the texture coefficient TC (1,2,11) is4.0 or more, the texture coefficient of the (1,2,11) plane is greaterthan the TC of any of the other crystal planes in light of the pointthat the total of the TCs of the respective crystal planes is 8.0 ormore. In other words, if the texture coefficient TC (1,2,11) is 4.0 ormore, the α-type aluminum oxide layer has the most preferentialorientation of the (1,2,11) plane. In light of the above, the coatedcutting tool of the present embodiment brings about the suppression ofthe progress of chemical reaction wear and the enhancement of wearresistance and further brings about the enhancement of fractureresistance, and, as a result, the tool life of the coated cutting toolcan be extended.

The average thickness of the α-type aluminum oxide layer of the presentembodiment is preferably from 1.0 μm or more to 15.0 μm or less. If theaverage thickness of the α-type aluminum oxide layer is 1.0 μm or more,this indicates the tendency of the crater wear resistance in the rakesurface of the coated cutting tool to be further improved, and if suchaverage thickness is 15.0 μm or less, this indicates the tendency of thefracture resistance of the coated cutting tool to be further improved asthe peeling of the coating layer is further suppressed. From the sameperspective, the average thickness of the α-type aluminum oxide layer ispreferably from 1.5 μm or more to 12.0 μm or less, and is furtherpreferably from 3.0 μm or more to 10.0 μm or less.

In the present embodiment, the residual stress value in a (1,1,6) planeof the α-type aluminum oxide layer is, at least in part thereof,preferably from −300 MPa or higher to 300 MPa or lower. If the residualstress value is −300 MPa or higher, this indicates the tendency of thewear resistance to be improved because the progress of wear—which startsfrom the time when particles fall off from the α-type aluminum oxidelayer—can be further suppressed. Further, if the residual stress valueis 300 MPa or lower, this indicates the tendency of the fractureresistance of the coated cutting tool to be further improved because thegeneration of cracking in the α-type aluminum oxide layer can be furthersuppressed. From the same perspective, the residual stress value in the(1,1,6) plane of the α-type aluminum oxide layer is more preferably from−250 MPa or higher to 250 MPa or lower.

Herein, the term “at least in part thereof” indicates that, it is notnecessary to satisfy, in the entire α-type aluminum oxide layer, theabove residual stress value range in the (1,1,6) plane of the α-typealuminum oxide layer, and such term also indicates that it is onlyrequired to satisfy the above residual stress value range in the (1,1,6)plane of the α-type aluminum oxide layer in a specific area such as arake surface.

The residual stress value of the α-type aluminum oxide layer can bemeasured by a sin²φ method using an X-ray stress measuring apparatus. Itis preferable to measure, via the sin²φ method, the residual stresses atany three points included in the coating layer and to obtain thearithmetic mean of the residual stresses at such three points. Any threepoints, serving as measurement locations, in the α-type aluminum oxidelayer are preferably selected in such a way as to be 0.1 mm or moreapart from one another.

In order to measure the residual stress value in the (1,1,6) plane ofthe α-type aluminum oxide layer, the (1,1,6) plane of the α-typealuminum oxide layer which serves as a measurement subject is selectedfor measurement. More specifically, a sample in which an α-type aluminumoxide layer is formed is subjected to analysis with an X-raydiffractometer. Then, an examination is conducted regarding variationsin the diffraction angle of the (1,1,6) plane when a change is made toan angle φ formed by a sample plane normal and a lattice plane normal.

The α-type aluminum oxide layer is a layer comprised of α-type aluminumoxide. However, such α-type aluminum oxide layer may contain a verysmall amount of components other than α-type aluminum oxide, as long asit comprises the configuration of the present embodiment and providesthe operation and effects of the present invention.

The coating layer of the present embodiment preferably comprises a TiCNlayer between the substrate and the α-type aluminum oxide layer, as thisimproves wear resistance. When regarding a peak intensity for a (2,2,0)plane in X-ray diffraction of the TiCN layer as I₂₂₀ and also regardinga peak intensity for a (3,1,1) plane in X-ray diffraction of the TiCNlayer as I₃₁₁, a ratio I₃₁₁/I₂₂₀ of I₃₁₁ to I₂₂₀ is preferably from 1.5or more to 20.0 or less. If the I₃₁₁/I₂₂₀ in the TiCN layer is from 1.5or more to 20.0 or less, this indicates the tendency of the adhesion ofthe TiCN layer to the α-type aluminum oxide layer to be furtherimproved. Further, it is preferable that, if the I₃₁₁/I₂₂₀ in the TiCNlayer is from 1.5 or more to 20.0 or less, this indicates the tendencyof the texture coefficient TC (1,2,11) in the α-type aluminum oxidelayer to have a greater value. From the same perspective, the ratioI₃₁₁/I₂₂₀ in the TiCN layer is more preferably from 2.5 or more to 20.0or less.

The peak intensity for each crystal plane of the α-type aluminum oxidelayer and the TiCN layer can be measured using a commercially availableX-ray diffractometer. For instance, using model: RINT TTR IIImanufactured by Rigaku Corporation was used. an X-ray diffractionmeasurement by means of a 2θ/θ focusing optical system with Cu-Kαradiation is performed under the following conditions: an output: 50 kV,250 mA; an incident-side solar slit: 5°; a divergence longitudinal slit:2/3°; a divergence longitudinal limit slit: 5 mm; a scattering slit:2/3°; a light-receiving side solar slit: 5°; a light-receiving slit: 0.3mm; a BENT monochromator; a light-receiving monochrome slit: 0.8 mm; asampling width: 0.01°; a scan speed: 4°/min; and a 2θ measurement range:20°-155°, whereby the peak intensity for each crystal plane can bemeasured. When obtaining the peak intensity for each crystal plane froman X-ray diffraction pattern, analytic software included with the X-raydiffractometer may be used. With such analytic software, backgroundprocessing and Kα₂ peak removal are conducted using cubic spline, andprofile fitting is conducted using Pearson-VII function, whereby eachpeak intensity can be obtained. It should be noted that, when variouslayers are formed between the α-type aluminum oxide layer and thesubstrate, each peak intensity can be measured by a thin-film X-raydiffraction method in order to avoid the influence of the layer.Further, when various layers are formed on a side opposite to thesubstrate across the α-type aluminum oxide layer, an X-ray diffractionmeasurement may be performed after the removal of such various layersvia buffing.

The average thickness of the TiCN layer of the present embodiment ispreferably from 2.0 μm or more to 20.0 μm or less. If the averagethickness of the TiCN layer is 2.0 μm or more, this indicates thetendency of the wear resistance of the coated cutting tool to be furtherimproved, and, if such average thickness is 20.0 μm or less, thisindicates the tendency of the fracture resistance of the coated cuttingtool to be further improved as the peeling of the coating layer isfurther suppressed. From the same perspective, the average thickness ofthe TiCN layer is more preferably from 5.0 μm or more to 15.0 μm orless.

The TiCN layer is a layer comprised of TiCN. However, such TiCN layermay contain a very small amount of components other than TiCN, as longas it comprises the above-described configuration and provides theoperation and effects of the TiCN layer.

The coating layer of the present embodiment preferably includes, betweenthe TiCN layer and the α-type aluminum oxide layer, an intermediatelayer comprised of a compound of at least one kind selected from thegroup consisting of a Ti carbonate, a Ti oxynitride and a Ticarboxynitride as the adhesion is further improved. The averagethickness of such intermediate layer is preferably from 0.2 μm or moreto 1.5 μm or less. This is preferable in that: if the average thicknessof the intermediate layer is 0.2 μm or more, this indicates the tendencyof the adhesion to be further improved; and, if such average thicknessis 1.5 μm or less, this indicates the tendency of the texturecoefficient TC (1,2,11) of the (1,2,11) plane in the α-type aluminumoxide layer to have a greater value.

The intermediate layer is a layer comprised of a compound of at leastone kind selected from the group consisting of a Ti carbonate, a Tioxynitride and a Ti carboxynitride. However, such intermediate layer maycontain a very small amount of components other than the above compound,as long as it comprises the above-described configuration and providesthe operation and effects of the intermediate layer.

The coating layer of the present embodiment preferably comprises a TiNlayer as an outermost layer on a side opposite to the substrate as thismakes it possible to confirm the usage state, such as whether or not thecoated cutting tool has been used, thereby leading to excellentvisibility. The average thickness of the TiN layer is preferably from0.2 μm or more to 1.0 μm or less. This is preferable in that: if theaverage thickness of the TiN layer is 0.2 μm or more, this provides theeffect of further suppressing the falling of particles from the α-typealuminum oxide layer; and, if such average thickness is 1.0 μm or less,the fracture resistance of the coated cutting tool is improved.

The coating layer of the present embodiment preferably comprises,between the substrate and the TiCN layer, a TiN layer serving as alowermost layer in the coating layer, as this leads to adhesion beingimproved. The average thickness of this TiN layer is preferably from 0.1μm or more to 0.5 μm or less. If the average thickness of the TiN layeris 0.1 μm or more, this indicates the tendency of the adhesion to befurther improved as the TiN layer has a more uniform structure.Meanwhile, if the average thickness of the TiN layer is 0.5 μm or less,this indicates the tendency of the fracture resistance to be furtherenhanced as the TiN layer, being the lowermost layer, is furtherprevented from serving as a starting point of peeling.

The TiN layers respectively serving as the outermost layer and thelowermost layer are each a layer comprised of TiN. However, such TiNlayers may each contain a very small amount of components other thanTiN, as long as they respectively comprise the above-describedconfigurations and provide the operation and effects of the outermostlayer and the lowermost layer.

Examples of a method of forming layers that constitute a coating layerin a coated cutting tool according to the present invention include themethod set forth below. However, such method of forming layers is notlimited thereto.

For instance, a TiN layer can be formed by chemical vapor depositionwith a raw material gas composition of TiCl₄: from 5.0 mol % or more to10.0 mol % or less, N₂: from 20 mol % or more to 60 mol % or less, andH₂: the balance, a temperature of from 850° C. or higher to 920° C. orlower, and a pressure of from 100 hPa or higher to 400 hPa or lower.

A TiCN layer can be formed by chemical vapor deposition with a rawmaterial gas composition of TiCl₄: from 8.0 mol % or more to 18.0 mol %or less, CH₃CN: from 1.0 mol % or more to 3.0 mol % or less, and H₂: thebalance, a temperature of from 900° C. or higher to 940° C. or lower,and a pressure of from 60 hPa or higher to 80 hPa or lower. At thistime, the peak intensity ratio I₃₁₁/I₂₂₀ of the TiCN layer can beadjusted so as to fall within a range of from 1.5 or more to 20.0 orless by controlling the molar ratio of TiCl₄ to CH₃CN, i.e.,TiCl₄/CH₃CN, so as to be from 4.0 or more to 8.0 or less.

A TiCNO layer, being a layer comprised of a Ti carboxynitride, can beformed by chemical vapor deposition with a raw material gas compositionof TiCl₄: from 3.0 mol % or more to 5.0 mol % or less, CO: from 0.4 mol% or more to 1.0 mol % or less, N₂: from 30 mol % or more to 40 mol % orless, and H₂: the balance, a temperature of from 975° C. or higher to1,025° C. or lower, and a pressure of from 90 hPa or higher to 110 hPaor lower.

A TiCO layer, being a layer comprised of a Ti carbonate, can be formedby chemical vapor deposition with a raw material gas composition ofTiCl₄: from 0.5 mol % or more to 1.5 mol % or less, CO: from 2.0 mol %or more to 4.0 mol % or less, and H₂: the balance, a temperature of from975° C. or higher to 1,025° C. or lower, and a pressure of from 60 hPaor higher to 100 hPa or lower.

In the present embodiment, a coated cutting tool which involves thecontrolled orientation (orientation relationship) of an α-type aluminumoxide layer can be obtained by, for example, the method set forth below.

Firstly, one or more layers selected from the group consisting of a TiCNlayer, if necessary, a TiN layer, also if necessary, and theintermediate layer is(are) formed on a surface of a substrate. Next,from among the above layers, a surface of a layer which is most distantfrom the substrate is oxidized. Thereafter, a nucleus of an α-typealuminum oxide layer is formed on the surface of the layer which is mostdistant from the substrate, and an α-type aluminum oxide layer is thenformed in the state in which such nucleus has been formed. Further, asneeded, a TiN layer may be formed on a surface of the α-type aluminumoxide layer.

More specifically, the oxidation of the surface of the layer which ismost distant from the substrate is performed under the conditions of araw material gas composition of CO₂: from 0.1 mol % or more to 1.0 mol %or less, C₂H₄: from 0.05 mol % or more to 0.2 mol % or less, and H₂: thebalance, a temperature of from 900° C. or higher to 950° C. or lower,and a pressure of from 50 hPa or higher to 70 hPa or lower. Here, theoxidation time is preferably from 5 minutes or more to 10 minutes orless.

Thereafter, the nucleus of the α-type aluminum oxide layer is formed bychemical vapor deposition with a raw material gas composition of AlCl₃:from 2.0 mol % or more to 5.0 mol % or less, 002: from 2.5 mol % or moreto 4.0 mol % or less, HCl: from 2.0 mol % or more to 3.0 mol % or less,C₃H₆: from 0.05 mol % or more to 0.2 mol % or less, and H₂: the balance,a temperature of from 970° C. or higher to 1,030° C. or lower, and apressure of from 60 hPa or higher to 80 hPa or lower.

The α-type aluminum oxide layer is then formed by chemical vapordeposition with a raw material gas composition of AlCl₃: from 2.0 mol %or more to 5.0 mol % or less, CO₂: from 2.5 mol % or more to 4.0 mol %or less, HCl: from 2.0 mol % or more to 3.0 mol % or less, H₂S: from0.15 mol % or more to 0.25 mol % or less, and H₂: the balance, atemperature of from 970° C. or higher to 1,030° C. or lower, and apressure of from 60 hPa or higher to 80 hPa or lower.

As described above, a surface of the TiN layer, the TiCN layer or theintermediate layer is oxidized, the nucleus of the α-type aluminum oxidelayer is then formed, and the α-type aluminum oxide layer is then formedwith normal conditions, thereby making it possible to obtain an α-typealuminum oxide layer with a texture coefficient TC (1,2,11) of 1.4 ormore. At this time, it is preferable that a surface of a TiCN layer witha peak intensity ratio I₃₁₁/I₂₂₀ of from 1.5 or more to 20.0 or less isoxidized, and that a nucleus of an α-type aluminum oxide layer is thenformed thereon, because this indicates the tendency of the texturecoefficient TC (1,2,11) of the α-type aluminum oxide layer to beincreased.

After the formation of the coating layer, dry shot blasting, wet shotblasting or shot peening is performed thereon, and the conditions areadjusted, thereby making it possible to control the residual stressvalue in a (1,1,6) plane of the α-type aluminum oxide layer. Forinstance, as to the conditions for dry shot blasting, a shot materialmay be shot onto a surface of the coating layer at a shot velocity offrom 50 m/sec or more to 80 m/sec or less and for a shot time of from0.5 minutes or more to 3 minutes or less so as to achieve a shot angleof from 30° or more to 70° or less. From the perspective of easilycontrolling the residual stress value so as to fall within the aboverange, the shot material (medium) in dry shot blasting is preferably amaterial(s) of one or more kinds, each of which has an average particlesize of from 100 μm or more to 150 μm or less and is(are) selected fromthe group consisting of Al₂O₃ and ZrO₂.

The thickness of each layer in the coating layer of the coated cuttingtool of the present embodiment can be measured by observing across-sectional structure of the coated cutting tool, using an opticalmicroscope, a scanning electron microscope (SEM), a field emissionscanning electron microscope (FE-SEM), or the like. It should be notedthat, as to the average thickness of each layer in the coated cuttingtool of the present embodiment, such average thickness can be obtainedby: measuring the thickness of each layer at three or more locationsnear the position 50 μm from the edge, toward the center of the rakesurface of the coated cutting tool; and calculating the arithmetic meanof the resulting measurements. Further, the composition of each layercan be measured from a cross-sectional structure of the coated cuttingtool of the present embodiment, using an energy-dispersive X-rayspectroscope (EDS), a wavelength-dispersive X-ray spectroscope (WDS) orthe like.

EXAMPLES

Although the present invention will be described in further detailbelow, with examples, the present invention is not limited to suchexamples.

A cemented carbide cutting insert with a shape of JIS certifiedCNMA120412 and a composition of 93.1WC-6.400-0.5Cr₃C₂ (mass %) wasprepared as a substrate. The edge of such substrate was subjected toround honing by means of an SiC brush, and a surface of the substratewas then washed.

After the substrate surface was washed, a coating layer was formed bychemical vapor deposition. As to invention samples 1 to 17, firstly, thesubstrate was inserted into an external heating chemical vapordeposition apparatus, and a lowermost layer, whose composition is shownin Table 6, was formed on the substrate surface so as to have theaverage thickness shown in Table 6 under the raw material gascomposition, temperature and pressure conditions shown in Table 1. Then,a TiCN layer, whose composition is shown in Table 6, was formed on thesurface of the lowermost layer so as to have the average thickness shownin Table 6 under the raw material gas composition, temperature andpressure conditions shown in Table 2. Next, an intermediate layer, whosecomposition is shown in Table 6, was formed on the surface of the TiCNlayer so as to have the average thickness shown in Table 6 under the rawmaterial gas composition, temperature and pressure conditions shown inTable 1. Thereafter, a surface of the intermediate layer was oxidizedfor the time shown in Table 3, under the raw material gas composition,temperature and pressure conditions shown in Table 3. Then, a nucleus ofα-type aluminum oxide was formed on the oxidized surface of theintermediate layer under the raw material gas composition, temperatureand pressure conditions concerning the “nucleus formation conditions”shown in Table 4. Further, an α-type aluminum oxide layer, whosecomposition is shown in Table 6, was formed on the surface of theintermediate layer and the surface of the nucleus of α-type aluminumoxide so as to have the average thickness shown in Table 6 under the rawmaterial gas composition, temperature and pressure conditions concerningthe “deposition conditions” shown in Table 4. Lastly, an outermostlayer, whose composition is shown in Table 6, was formed on the surfaceof the α-type aluminum oxide layer so as to have the average thicknessshown in Table 6 under the raw material gas composition, temperature andpressure conditions shown in Table 1. As a result, the coated cuttingtools of invention samples 1 to 17 were obtained.

Meanwhile, as to comparative samples 1 to 14, firstly, the substrate wasinserted into an external heating chemical vapor deposition apparatus,and a lowermost layer, whose composition is shown in Table 6, was formedon the substrate surface so as to have the average thickness shown inTable 6 under the raw material gas composition, temperature and pressureconditions shown in Table 1. Then, a TiCN layer, whose composition isshown in Table 6, was formed on the surface of the lowermost layer so asto have the average thickness shown in Table 6 under the raw materialgas composition, temperature and pressure conditions shown in Table 2.Next, an intermediate layer, whose composition is shown in Table 6, wasformed on the surface of the TiCN layer so as to have the averagethickness shown in Table 6 under the raw material gas composition,temperature and pressure conditions shown in Table 1. Thereafter, thesurface of the intermediate layer was oxidized for the time shown inTable 3, under the raw material gas composition, temperature andpressure conditions shown in Table 3. Then, a nucleus of α-type aluminumoxide was formed on the oxidized surface of the intermediate layer underthe raw material gas composition, temperature and pressure conditionsconcerning the “nucleus formation conditions” shown in Table 5. Further,an α-type aluminum oxide layer, whose composition is shown in Table 6,was formed on the surface of the intermediate layer and the surface ofthe nucleus of α-type aluminum oxide so as to have the average thicknessshown in Table 6 under the raw material gas composition, temperature andpressure conditions concerning the “deposition conditions” shown inTable 5. Lastly, an outermost layer, whose composition is shown in Table6, was formed on the surface of the α-type aluminum oxide layer so as tohave the average thickness shown in Table 6 under the raw material gascomposition, temperature and pressure conditions shown in Table 1. As aresult, the coated cutting tools of comparative samples 1 to 14 wereobtained.

The thickness of each layer of each of the samples was obtained as setforth below. That is, using an FE-SEM, the average thickness wasobtained by: measuring the thickness of each layer, from each of thecross-sectional surfaces at three locations near the position 50 μm fromthe edge of the coated cutting tool, toward the center of the rakesurface thereof; and calculating the arithmetic mean of the resultingmeasurements. Using an EDS, the composition of each layer of theobtained sample was measured from the cross-sectional surface near theposition at most 50 μm from the edge of the coated cutting tool, towardthe center of the rake surface thereof.

TABLE 1 Each layer Temperature Pressure Raw material gas compositioncomposition (° C.) (hPa) (mol %) TiN 900 400 TiCl₄: 7.5%, N₂: 40.0%, H₂:52.5% TiC 1,000 75 TiCl₄: 2.4%, CH₄: 4.6%, H₂: 93.0% TiCNO 1,000 100TiCl₄: 3.5%, CO: 0.7%, N₂: 35.5%, H₂: 60.3% TiCO 1,000 80 TiCl₄: 1.3%,CO: 2.7%, H₂: 96.0%

TABLE 2 Temperature Pressure Raw material gas composition Sample No. (°C.) (hPa) (mol %) Invention 920 60 TiCl₄: 11.0%, CH₃CN: 2.5%, H₂: sample1 86.5% Invention 920 70 TiCl₄: 12.0%, CH₃CN: 2.2%, H₂: sample 2 85.8%Invention 890 70 TiCl₄: 12.0%, CH₃CN: 2.2%, H₂: sample 3 85.8% Invention920 80 TiCl₄: 10.0%, CH₃CN: 1.4%, H₂: sample 4 88.6% Invention 920 70TiCl₄: 12.0%, CH₃CN: 2.2%, H₂: sample 5 85.8% Invention 920 80 TiCl₄:12.0%, CH₃CN: 3.0%, H₂: sample 6 85.0% Invention 920 70 TiCl₄: 12.0%,CH₃CN: 2.2%, H₂: sample 7 85.8% Invention 920 70 TiCl₄: 8.0%, CH₃CN:2.0%, H₂: sample 8 90.0% Invention 940 70 TiCl₄: 12.0%, CH₃CN: 2.2%, H₂:sample 9 85.8% Invention 920 70 TiCl₄: 11.0%, CH₃CN: 2.0%, H₂: sample 1087.0% Invention 920 70 TiCl₄: 18.0%, CH₃CN: 2.3%, H₂: sample 11 79.7%Invention 920 70 TiCl₄: 12.0%, CH₃CN: 2.2%, H₂: sample 12 85.8%Invention 920 70 TiCl₄: 12.0%, CH₃CN: 2.2%, H₂: sample 13 85.8%Invention 920 70 TiCl₄: 12.0%, CH₃CN: 2.2%, H₂: sample 14 85.8%Invention 920 70 TiCl₄: 12.0%, CH₃CN: 2.2%, H₂: sample 15 85.8%Invention 920 70 TiCl₄: 12.0%, CH₃CN: 2.2%, H₂: sample 16 85.8%Invention 920 60 TiCl₄: 11.0%, CH₃CN: 2.5%, H₂: sample 17 86.5%Comparative 920 70 TiCl₄: 11.0%, CH₃CN: 2.5%, H₂: sample 1 86.5%Comparative 920 70 TiCl₄: 8.0%, CH₃CN: 2.0%, H₂: sample 2 90.0%Comparative 890 70 TiCl₄: 10.0%, CH₃CN: 2.0%, H₂: sample 3 88.0%Comparative 940 70 TiCl₄: 10.0%, CH₃CN: 2.0%, H₂: sample 4 88.0%Comparative 920 70 TiCl₄: 10.0%, CH₃CN: 2.2%, H₂: sample 5 87.8%Comparative 920 70 TiCl₄: 12.0%, CH₃CN: 2.2%, H₂: sample 6 85.8%Comparative 920 70 TiCl₄: 14.0%, CH₃CN: 3.0%, H₂: sample 7 83.0%Comparative 920 70 TiCl₄: 14.0%, CH₃CN: 2.7%, H₂: sample 8 83.3%Comparative 920 60 TiCl₄: 8.0%, CH₃CN: 1.5%, H₂: sample 9 90.5%Comparative 920 90 TiCl₄: 10.0%, CH₃CN: 1.4%, H₂: sample 10 88.6%Comparative 920 70 TiCl₄: 12.0%, CH₃CN: 2.2%, H₂: sample 11 85.8%Comparative 920 70 TiCl₄: 12.0%, CH₃CN: 2.2%, H₂: sample 12 85.8%Comparative 920 70 TiCl₄: 12.0%, CH₃CN: 2.2%, H₂: sample 13 85.8%Comparative 920 60 TiCl₄: 11.0%, CH₃CN: 2.5%, H₂: sample 14 86.5%

TABLE 3 Temperature Pressure Raw material gas composition Hour SampleNo. (° C.) (hPa) (mol %) (min) Invention 930 50 CO₂: 0.5%, C₂H₄: 0.1%,H₂: 5 sample 1 99.4% Invention 930 60 CO₂: 0.7%, C₂H₄: 0.1%, H₂: 6sample 2 99.2% Invention 930 60 CO₂: 0.5%, C₂H₄: 0.15%, H₂: 8 sample 399.35% Invention 950 60 CO₂: 0.5%, C₂H₄: 0.1%, H₂: 9 sample 4 99.4%Invention 930 70 CO₂: 0.7%, C₂H₄: 0.1%, H₂: 7 sample 5 99.2% Invention900 60 CO₂: 1.0%, C₂H₄: 0.1%, H₂: 6 sample 6 98.9% Invention 930 60 CO₂:0.5%, C₂H₄: 0.1%, H₂: 6 sample 7 99.4% Invention 900 60 CO₂: 0.1%, C₂H₄:0.1%, H₂: 5 sample 8 99.8% Invention 930 60 CO₂: 0.7%, C₂H₄: 0.1%, H₂: 6sample 9 99.2% Invention 930 50 CO₂: 0.7%, C₂H₄: 0.1%, H₂: 8 sample 1099.2% Invention 950 60 CO₂: 0.5%, C₂H₄: 0.2%, H₂: 10 sample 11 99.3%Invention 930 50 CO₂: 0.5%, C₂H₄: 0.1%, H₂: 5 sample 12 99.4% Invention930 60 CO₂: 0.7%, C₂H₄: 0.1%, H₂: 6 sample 13 99.2% Invention 950 60CO₂: 0.5%, C₂H₄: 0.2%, H₂: 10 sample 14 99.3% Invention 930 60 CO₂:0.7%, C₂H₄: 0.1%, H₂: 6 sample 15 99.2% Invention 930 60 CO₂: 0.7%,C₂H₄: 0.1%, H₂: 6 sample 16 99.2% Invention 930 60 CO₂: 0.7%, C₂H₄:0.1%, H₂: 6 sample 17 99.2% Comparative 930 60 CO₂: 0.7%, H₂: 99.3% 5sample 1 Comparative 930 50 CO₂: 0.7%, H₂: 99.3% 7 sample 2 Comparative930 60 CO₂: 0.9%, H₂: 99.1% 5 sample 3 Comparative 930 60 CO₂: 0.1%, H₂:99.9% 10 sample 4 Comparative 930 70 CO₂: 0.5%, H₂: 99.5% 5 sample 5Comparative 930 60 CO₂: 0.2%, C₂H₄: 0.05%, H₂: 2 sample 6 99.75%Comparative 900 60 CO₂: 0.5%, H₂: 99.5% 5 sample 7 Comparative 930 60CO₂: 0.7%, H₂: 99.3% 6 sample 8 Comparative 930 60 CO₂: 0.7%, H₂: 99.3%5 sample 9 Comparative 950 60 CO₂: 0.5%, H₂: 99.5% 8 sample 10Comparative 930 60 CO₂: 0.7%, H₂: 99.3% 5 sample 11 Comparative 930 60CO₂: 0.7%, H₂: 99.3% 5 sample 12 Comparative 930 60 CO₂: 0.7%, H₂: 99.3%5 sample 13 Comparative 930 60 CO₂: 0.7%, H₂: 99.3% 5 sample 14

TABLE 4 Nucleus formation conditions Deposition conditions SampleTemperature Pressure Raw material gas composition Temperature PressureRaw material gas composition No. (° C.) (hPa) (mol %) (° C.) (hPa) (mol%) Invention 1,000 60 AlCl₃: 3.2%, CO₂: 3.4%, HCl: 2.5%, 1,000 60 AlCl₃:2.4%, CO₂: 2.6%, HCl: 2.7%, sample 1 C₃H₆: 0.1%, H₂: 90.8% H₂S: 0.2%,H₂: 92.1% Invention 1,000 70 AlCl₃: 4.2%, CO₂: 3.0%, HCl: 2.5%, 1,000 70AlCl₃: 2.8%, CO₂: 2.6%, HCl: 2.5%, sample 2 C₃H₆: 0.15%, H₂: 90.15% H₂S:0.2%, H₂: 91.9% Invention 1,000 70 AlCl₃: 4.2%, CO₂: 3.0%, HCl: 2.5%,1,000 70 AlCl₃: 2.8%, CO₂: 2.6%, HCl: 2.5%, sample 3 C₃H₆: 0.15%, H₂:90.15% H₂S: 0.2%, H₂: 91.9% Invention 1,020 70 AlCl₃: 2.6%, CO₂: 3.4%,HCl: 2.5%, 1,020 70 AlCl₃: 4.8%, CO₂: 2.5%, HCl: 2.7%, sample 4 C₃H₆:0.2%, H₂: 91.3% H₂S: 0.15%, H₂: 89.85% Invention 1,000 70 AlCl₃: 3.2%,CO₂: 3.4%, HCl: 2.5%, 1,000 70 AlCl₃: 2.8%, CO₂: 2.6%, HCl: 2.5%, sample5 C₃H₆: 0.1%, H₂: 90.8% H₂S: 0.2%, H₂: 91.9% Invention 970 70 AlCl₃:5.0%, CO₂: 2.5%, HCl: 2.4%, 970 70 AlCl₃: 2.0%, CO₂: 4.0%, HCl: 2.0%,sample 6 C₃H₆: 0.1%, H₂: 90.0% H₂S: 0.25%, H₂: 91.75% Invention 1,000 80AlCl₃: 3.2%, CO₂: 3.4%, HCl: 2.5%, 1,000 80 AlCl₃: 2.4%, CO₂: 2.6%, HCl:2.7%, sample 7 C₃H₆: 0.1%, H₂: 90.8% H₂S: 0.2%, H₂: 92.1% Invention 97060 AlCl₃: 3.2%, CO₂: 3.4%, HCl: 2.5%, 970 60 AlCl₃: 2.4%, CO₂: 2.6%,HCl: 2.7%, sample 8 C₃H₆: 0.1%, H₂: 90.8% H₂S: 0.2%, H₂: 92.1% Invention1,000 60 AlCl₃: 3.2%, CO₂: 3.4%, HCl: 2.5%, 1,000 60 AlCl_(3:) 2.8%,CO₂: 2.6%, HCl: 2.5%, sample 9 C₃H₆: 0.1%, H₂: 90.8% H₂S: 0.2%, H₂:91.9% Invention 1,000 70 AlCl₃: 2.0%, CO₂: 4.0%, HCl: 2.0%, 1,000 70AlCl₃: 2.8%, CO₂: 2.6%, HCl: 2.5%, sample 10 C₃H₆: 0.1%, H₂: 91.9% H₂S:0.2%, H₂: 91.9% Invention 1,020 70 AlCl₃: 2.6%, CO₂: 3.4%, HCl: 2.5%,1,020 70 AlCl₃: 4.8%, CO₂: 2.5%, HCl: 2.7%, sample 11 C₃H₆: 0.2%, H₂:91.3% H₂S: 0.15%, H₂: 89.85% Invention 1,000 60 AlCl₃: 3.2%, CO₂: 3.4%,HCl: 2.5%, 1,000 60 AlCl₃: 2.4%, CO₂: 2.6%, HCl: 2.7%, sample 12 C₃H₆:0.1%, H₂: 90.8% H₂S: 0.2%, H₂: 92.1% Invention 1,000 70 AlCl₃: 4.2%,CO₂: 3.0%, HCl: 2.5%, 1,000 70 AlCl₃: 2.8%, CO₂: 2.6%, HCl: 2.5%, sample13 C₃H₆: 0.15%, H₂: 90.15% H₂S: 0.2%, H₂: 91.9% Invention 1,020 70AlCl₃: 2.6%, CO₂: 3.4%, HCl: 2.5%, 1,020 70 AlCl₃: 4.8%, CO₂: 2.5%, HCl:2.7%, sample 14 C₃H₆: 0.2%, H₂: 91.3% H₂S: 0.15%, H₂: 89.85% Invention1,000 70 AlCl₃: 4.2%, CO₂: 3.0%, HCl: 2.5%, 1,000 70 AlCl₃: 2.8%, CO₂:2.6%, HCl: 2.5%, sample 15 C₃H₆: 0.15%, H₂: 90.15% H₂S: 0.2%, H₂: 91.9%Invention 1,000 70 AlCl₃: 4.2%, CO₂: 3.0%, HCl: 2.5%, 1,000 70 AlCl₃:2.8%, CO₂: 2.6%, HCl: 2.5%, sample 16 C₃H₆: 0.15%, H₂: 90.15% H₂S: 0.2%,H₂: 91.9% ention 1,000 70 AlCl₃: 4.2%, CO₂: 3.0%, HCl: 2.5%, 1,000 70AlCl₃: 2.8%, CO₂: 2.6%, HCl: 2.5%, sample 17 C₃H₆: 0.15%, H₂: 90.15%H₂S: 0.2%, H₂: 91.9%

TABLE 5 Nucleus formation conditions Deposition conditions TemperaturePressure Raw material gas composition Temperature Pressure Raw materialgas composition Sample No. (° C.) (hPa) (mol %) (° C.) (hPa) (mol %)Comparative 1,000 60 AlCl₃: 2.4%, CO₂: 3.6%, HCl: 2.6%, 1,000 60 AlCl₃:2.8%, CO₂: 2.6%, HCl: 2.5%, sample 1 H₂: 91.4% H₂S: 0.2%, H₂: 91.9%Comparative 1,000 70 AlCl₃: 2.4%, CO₂: 3.6%, HCl: 2.6%, 1,000 70 AlCl₃:2.4%, CO₂: 2.6%, HCl: 2.7%, sample 2 H₂: 91.4% H₂S: 0.2%, H₂: 92.1%Comparative 1,000 70 AlCl₃: 2.4%, CO₂: 3.6%, HCl: 2.6%, 1,000 70 AlCl₃:2.4%, CO₂: 2.6%, HCl: 2.7%, sample 3 C₃H₆: 0.2%, H₂: 90.9% H₂S: 0.2%,H₂: 92.1% Comparative 1,020 70 AlCl₃: 2.4%, CO₂: 3.6%, HCl: 2.6%, 1,02070 AlCl₃: 4.6%, CO₂: 2.5%, HCl: 2.4%, sample 4 H₂: 91.4% H₂S: 0.15%, H₂:90.35% Comparative 1,000 70 AlCl₃: 2.4%, CO₂: 3.6%, HCl: 2.6%, 1,000 70AlCl₃: 2.4%, CO₂: 2.6%, HCl: 2.7%, samples H₂: 91.4% H₂S: 0.2%, H₂:92.1% Comparative 1,000 70 AlCl₃: 2.4%, CO₂: 3.6%, HCl: 2.6%, 1,000 70AlCl₃: 2.4%, CO₂: 2.6%, HCl: 2.7%, sample 6 C₃H₆: 0.1%, H₂: 91.3% H₂S:0.2%, H₂: 92.1% Comparative 1,000 80 AlCl₃: 4.8%, CO₂: 2.5%, HCl: 2.2%,1,000 80 AlCl₃: 2.0%, CO₂: 4.0%, HCl: 1.5%, sample 7 H₂: 90.5% H₂S:0.25%, H₂: 92.25% Comparative 970 60 AlCl₃: 2.4%, CO₂: 3.6%, HCl: 2.6%,970 60 AlCl₃: 2.8%, CO₂: 2.6%, HCl: 2.5%, sample 8 H₂: 91.4% H₂S: 0.2%,H₂: 91.9% Comparative 1,000 60 AlCl₃: 2.0%, CO₂: 4.0%, HCl: 3.5%, 1,00060 AlCl₃: 2.8%, CO₂: 2.6%, HCl: 2.5%, sample 9 H₂: 90.5% H₂S: 0.2%, H₂:91.9% Comparative 1,000 70 AlCl₃: 2.4%, CO₂: 3.6%, HCl: 2.6%, 1,000 70AlCl₃: 2.4%, CO₂: 2.6%, HCl: 2.7%, sample 10 H₂: 91.4% H₂S: 0.2%, H₂:92.1% Comparative 1,000 60 AlCl₃: 2.4%, CO₂: 3.6%, HCl: 2.6%, 1,000 60AlCl₃: 2.8%, CO₂: 2.6%, HCl: 2.5%, sample 11 H₂: 91.4% H₂S: 0.2%, H₂:91.9% Comparative 1,000 60 AlCl₃: 2.4%, CO₂: 3.6%, HCl: 2.6%, 1,000 60AlCl₃: 2.8%, CO₂: 2.6%, HCl: 2.5%, sample 12 H₂: 91.4% H₂S: 0.2%, H₂:91.9% Comparative 1,000 60 AlCl₃: 2.4%, CO₂: 3.6%, HCl: 2.6%, 1,000 60AlCl₃: 2.8%, CO₂: 2.6%, HCl: 2.5%, sample 13 H₂: 91.4% H₂S: 0.2%, H₂:91.9% Comparative 1,000 60 AlCl₃: 2.4%, CO₂: 3.6%, HCl: 2.6%, 1,000 60AlCl₃: 2.8%, CO₂: 2.6%, HCl: 2.5%, sample 14 H₂: 91.4% H₂S: 0.2%, H₂:91.9%

TABLE 6 Coating layer α-type aluminum Lowermost layer TiCN layerIntermediate layer oxide layer Outermost layer Average Average AverageAverage Average Total Compo- thickness Compo- thickness Compo- thicknessCrystal thickness Compo- thickness thickness Sample No. sition (μm)sition (μm) sition (μm) system (μm) sition (μm) (μm) Invention TiN 0.2TiCN 6.4 TiCO 0.3 α 5.0 TiN 0.3 12.2 sample 1 Invention TiN 0.2 TiCN 2.2TiCNO 0.3 α 12.0 TiN 0.3 15.0 sample 2 Invention TiN 0.3 TiCN 14.0 TiCO0.2 α 2.4 TiN 0.5 17.4 sample 3 Invention TiN 0.3 TiCN 20.0 TiCNO 0.1 α6.0 TiN 0.5 26.9 sample 4 Invention TiN 0.5 TiCN 10.0 TiCNO 0.3 α 7.5TiN 0.3 18.6 sample 5 Invention TiN 0.5 TiCN 7.2 TiCNO 0.7 α 7.5 TiN 0.516.4 sample 6 Invention TiN 1.2 TiCN 7.2 TiCO 0.3 α 10.0 TiN 0.2 18.9sample 7 Invention TiC 1.2 TiCN 10.0 TiCNO 0.5 α 10.0 TiN 0.3 22.0sample 8 Invention TiC 0.3 TiCN 5.0 TiCNO 0.5 α 5.5 TiN 0.2 11.5 sample9 Invention TiN 0.8 TiCN 5.0 TiCNO 1.0 α 15.0 TiN 0.2 22.0 sample 10Invention TiN 0.2 TiCN 3.0 TiCO 0.5 α 4.0 TiN 0.3 8.0 sample 11Invention TiN 0.2 TiCN 6.0 TiCNO 0.2 α 9.0 TiN 0.5 15.9 sample 12Invention TiN 0.2 TiCN 6.0 TiCNO 0.2 α 9.0 TiN 0.5 15.9 sample 13Invention TiN 0.2 TiCN 6.0 TiCNO 0.2 α 9.0 TiN 0.5 15.9 sample 14Invention TiN 0.2 TiCN 11.0 TiCNO 0.2 α 4.2 TiN 0.5 16.1 sample 15Invention TiN 0.2 TiCN 6.0 TiCNO 0.2 α 9.0 TiN 0.5 15.9 sample 16Invention TiN 0.2 TiCN 6.0 TiCNO 0.2 α 9.0 TiN 0.5 15.9 sample 17Comparative TiN 0.2 TiCN 6.4 TiCNO 0.5 α 5.5 TiN 0.3 12.9 sample 1Comparative TiN 0.2 TiCN 5.5 TiCNO 0.5 α 11.0 TiN 0.3 17.5 sample 2Comparative TiC 0.3 TiCN 20.0 TiCNO 0.1 α 3.0 TiN 0.5 23.9 sample 3Comparative TiC 0.3 TiCN 2.2 TiCNO 0.1 α 4.5 TiN 0.3 7.4 sample 4Comparative TiN 0.5 TiCN 5.5 TiCNO 0.2 α 6.5 TiN 0.3 13.0 sample 5Comparative TiN 0.5 TiCN 16.0 TiCNO 0.2 α 5.5 TiN 0.2 22.4 sample 6Comparative TiN 0.2 TiCN 6.4 TiCNO 0.3 α 15.0 TiN 0.3 22.2 sample 7Comparative TiN 0.8 TiCN 10.0 TiCO 0.3 α 10.0 TiN 0.3 21.4 sample 8Comparative TiN 1.2 TiCN 10.0 TiCNO 0.3 α 5.0 TiN 0.3 16.8 sample 9Comparative TiN 1.2 TiCN 5.0 TiCNO 1.0 α 10.0 TiN 0.3 17.5 sample 10Comparative TiN 0.2 TiCN 6.0 TiCNO 0.2 α 9.0 TiN 0.5 15.9 sample 11Comparative TiN 0.2 TiCN 11.0 TiCNO 0.2 α 4.2 TiN 0.5 16.1 sample 12Comparative TiN 0.2 TiCN 6.0 TiCNO 0.2 α 9.0 TiN 0.5 15.9 sample 13Comparative TiN 0.2 TiCN 6.0 TiCNO 0.2 α 9.0 TiN 0.5 15.9 sample 14

As to invention samples 1 to 17 and comparative samples 1 to 14, afterthe formation of the coating layer on the surface of the substrate, dryshot blasting was performed on a surface of the coating layer under theshot conditions shown in Table 7, using the shot material shown in Table7.

TABLE 7 Shot material Average Shot conditions particle Shot Shot Shotsize angle velocity time Sample No. Material (μm) (°) (m/sec) (min)Invention Al₂O₃ 120 50 70 2.5 sample 1 Invention Al₂O₃ 120 50 70 2.5sample 2 Invention Al₂O₃ 120 50 70 3.0 sample 3 Invention ZrO₂ 120 70 702.0 sample 4 Invention ZrO₂ 120 70 70 2.0 sample 5 Invention Al₂O₃ 12050 60 1.0 sample 6 Invention Al₂O₃ 120 50 60 1.0 sample 7 InventionAl₂O₃ 120 50 60 1.0 sample 8 Invention Al₂O₃ 100 40 50 1.0 sample 9Invention Al₂O₃ 150 70 70 3.0 sample 10 Invention Al₂O₃ 150 60 80 1.5sample 11 Invention Al₂O₃ 120 50 70 2.5 sample 12 Invention Al₂O₃ 120 5070 2.5 sample 13 Invention Al₂O₃ 120 50 70 2.5 sample 14 Invention Al₂O₃120 50 70 2.5 sample 15 Invention Al₂O₃ 120 50 60 1.0 sample 16Invention Al₂O₃ 120 50 70 2.5 sample 17 Comparative Al₂O₃ 120 50 70 2.5sample 1 Comparative Al₂O₃ 120 50 70 2.5 sample 2 Comparative Al₂O₃ 12050 70 3.0 sample 3 Comparative ZrO₂ 120 70 70 2.0 sample 4 ComparativeZrO₂ 120 70 70 2.0 sample 5 Comparative Al₂O₃ 120 50 60 1.0 sample 6Comparative Al₂O₃ 120 50 60 1.0 sample 7 Comparative Al2O₃ 120 50 60 1.0sample 8 Comparative Al₂O₃ 100 40 50 1.0 sample 9 Comparative Al₂O₃ 8040 50 1.0 sample 10 Comparative Al₂O₃ 120 50 70 2.5 sample 11Comparative Al₂O₃ 120 50 70 2.5 sample 12 Comparative Al₂O₃ 120 50 601.0 sample 13 Comparative Al₂O₃ 120 50 70 2.5 sample 14

As to the obtained samples, an X-ray diffraction measurement by means ofa 2θ/θ focusing optical system with Cu-Kα radiation was performed underthe following conditions: an output: 50 kV, 250 mA; an incident-sidesolar slit: 5°; a divergence longitudinal slit: 2/3°; a divergencelongitudinal limit slit: 5 mm; a scattering slit: 2/3°; alight-receiving side solar slit: 5°; a light-receiving slit: 0.3 mm; aBENT monochromator; a light-receiving monochrome slit: 0.8 mm; asampling width: 0.01°; a scan speed: 4°/min; and a 2θ measurement range:20°-155°. As to the apparatus, an X-ray diffractometer (model “RINT TTRIII”) manufactured by Rigaku Corporation was used. The peak intensityfor each crystal plane of the α-type aluminum oxide layer and the TiCNlayer was obtained from an X-ray diffraction pattern. A texturecoefficient TC (1,2,11) in the α-type aluminum oxide layer and anintensity ratio I₃₁₁/I₂₂₀ of the TiCN layer were obtained from theresulting peak intensity for each crystal plane. The results are shownin Table 8.

TABLE 8 α-type aluminum TiCN oxide layer layer Sample No. TC (1, 2, 11)I₃₁₁/I₂₂₀ Invention 4.5 2.1 sample 1 Invention 5.5 7.5 sample 2Invention 5.7 7.5 sample 3 Invention 6.4 13.2 sample 4 Invention 5.4 7.4sample 5 Invention 3.3 1.5 sample 6 Invention 4.6 7.6 sample 7 Invention1.5 1.1 sample 8 Invention 5.4 7.2 sample 9 Invention 5.5 7.5 sample 10Invention 7.1 19.4 sample 11 Invention 4.5 7.5 sample 12 Invention 5.57.5 sample 13 Invention 7.1 7.5 sample 14 Invention 5.5 7.5 sample 15Invention 5.5 7.5 sample 16 Invention 5.5 2.1 sample 17 Comparative 0.32.2 sample 1 Comparative 0.3 1.0 sample 2 Comparative 0.8 4.4 sample 3Comparative 0.5 4.2 sample 4 Comparative 0.4 3.6 sample 5 Comparative1.0 7.5 sample 6 Comparative 0.1 3.6 sample 7 Comparative 0.3 4.5 sample8 Comparative 0.2 4.5 sample 9 Comparative 0.5 13.0 sample 10Comparative 0.3 7.5 sample 11 Comparative 0.3 7.5 sample 12 Comparative0.3 7.5 sample 13 Comparative 0.3 2.1 sample 14

The residual stress value of the α-type aluminum oxide layer in each ofthe obtained samples was measured by a sin²φ method using an X-raystress measuring apparatus (model “RINT TTR III” manufactured by RigakuCorporation). The measurement results are shown in Table 9.

TABLE 9 α-type aluminum oxide layer Residual stress value whenmeasurement was performed with the selection of a (1, 1, 6) Sample No.plane (MPa) Invention −232 sample 1 Invention −224 sample 2 Invention−295 sample 3 Invention −106 sample 4 Invention −94 sample 5 Invention150 sample 6 Invention 168 sample 7 Invention 290 sample 8 Invention 272sample 9 Invention −410 sample 10 Invention 54 sample 11 Invention −230sample 12 Invention −230 sample 13 Invention −230 sample 14 Invention−230 sample 15 Invention 150 sample 16 Invention −230 sample 17Comparative −240 sample 1 Comparative −225 sample 2 Comparative −302sample 3 Comparative −114 sample 4 Comparative −105 sample 5 Comparative148 sample 6 Comparative 160 sample 7 Comparative 298 sample 8Comparative 278 sample 9 Comparative 350 sample 10 Comparative −230sample 11 Comparative −230 sample 12 Comparative 150 sample 13Comparative −230 sample 14

Cutting tests 1 and 2 were conducted using the obtained samples underthe following conditions. Cutting test 1 is a wear test for evaluatingwear resistance, and cutting test 2 is a fracture test for evaluatingfracture resistance. The results of the respective cutting tests areshown in Table 10.

[Cutting Test 1]

Workpiece material: S45C round bar

Cutting speed: 310 m/min

Feed: 0.30 mm/rev

Depth of cut: 2.0 mm

Coolant: used

Evaluation items: A time when a sample was fractured or had a maximumflank wear width of 0.2 mm was defined as the end of the tool life, andthe machining time to reach the end of the tool life was measured.

[Cutting Test 2]

Workpiece material: SCM415 round bar with two equidistant groovesextending in the length direction

Cutting speed: 240 m/min

Feed: 0.40 mm/rev

Depth of cut: 1.5 mm

Coolant: used

Evaluation items: A time when a sample was fractured was defined as theend of the tool life, and the number of shocks the sample had receiveduntil the end of the tool life was measured. The number of times thesample and the workpiece material were brought into contact with eachother was defined as the number of shocks, and the test was ended whenthe number of contacts reached 20,000 at a maximum. In other words, thenumber “20,000” for the tool life indicates that the end of the toollife was not reached even after the arrival of 20,000 shocks. It shouldbe noted that, as to each sample, five inserts were prepared and thenumber of shocks was measured for each of such cutting inserts, and thearithmetic mean was obtained from the measurements of the number ofshocks so as to serve as the tool life.

As to the machining time to reach the end of the tool life in cuttingtest 1 (wear test), evaluations were made with grade “A” for 30 minutesor more, grade “B” for 25 minutes or more and less than 30 minutes, andgrade “C” for less than 25 minutes. Further, as to the number of shocksuntil the end of the tool life in cutting test 2 (fracture test),evaluations were made with grade “A” for 15,000 or more, grade “B” for12,000 or more and less than 15,000, and grade “C” for less than 12,000.In such evaluations, “A” refers to excellent, “B” refers to good and “C”refers to inferior, meaning that a sample involving a larger number of“A”s or “B”s has more excellent cutting performance. The resultingevaluation results are shown in Table 10.

TABLE 10 Wear test Tool Fracture test life Damage Tool life Sample No.(min) Grade form (shocks) Grade Invention 25 B Normal 20,000 A sample 1wear Invention 31 A Normal 18,600 A sample 2 wear Invention 34 A Normal20,000 A sample 3 wear Invention 48 A Normal 15,400 A sample 4 wearInvention 35 A Normal 19,200 A sample 5 wear Invention 28 B Normal16,000 A sample 6 wear Invention 34 A Normal 15,800 A sample 7 wearInvention 32 A Normal 15,000 A sample 8 wear Invention 26 B Normal16,200 A sample 9 wear Invention 40 A Normal 17,900 A sample 10 wearInvention 25 B Normal 18,500 A sample 11 wear Invention 29 B Normal18,600 A sample 12 wear Invention 33 A Normal 19,200 A sample 13 wearInvention 38 A Normal 20,000 A sample 14 wear Invention 27 B Normal17,900 A sample 15 wear Invention 32 A Normal 16,100 A sample 16 wearInvention 30 A Normal 18,300 A sample 17 wear Comparative 17 C Normal19,600 A sample 1 wear Comparative 20 C Normal 15,200 A sample 2 wearComparative 22 C Normal 13,800 B sample 3 wear Comparative 10 C Normal17,800 A sample 4 wear Comparative 17 C Normal 17,400 A sample 5 wearComparative 23 C Normal 14,500 B sample 6 wear Comparative 20 C Normal14,000 B sample 7 wear Comparative 20 C Fracturing 7,400 C sample 8Comparative 20 C Normal 8,500 C sample 9 wear Comparative 23 CFracturing 9,600 C sample 10 Comparative 22 C Normal 14,000 B sample 11wear Comparative 19 C Normal 12,900 B sample 12 wear Comparative 18 CFracturing 9,100 C sample 13 Comparative 20 C Normal 13,400 B sample 14wear

The results of Table 10 show that each invention sample had grade “B” orhigher in the wear test and also show that each invention sample hadgrade “A” in the fracture test. Meanwhile, as to the evaluations on thecomparative samples, each comparative sample had grade “C” in either thewear test or the fracture test. In particular, in the wear test, eachinvention sample had grade “B” or higher and each comparative sample hadgrade “B” or “C.” Accordingly, it is apparent that the wear resistanceof each invention sample is more excellent than that of each comparativesample.

It is apparent from the above results that each invention sample hasexcellent wear resistance and fracture resistance, resulting in a longertool life.

The present application is based on the Japanese patent applicationfiled on Oct. 21, 2016 (JP Appl. 2016-206801), the content of which isincorporated herein by reference.

INDUSTRIAL APPLICABILITY

As to a coated cutting tool according to the present invention, suchcoated cutting tool does not involve a reduction in wear resistance andhas excellent fracture resistance, so that the tool life can be extendedmore than that involved in the prior art, and, from such perspective,the coated cutting tool has industrial applicability.

What is claimed is:
 1. A coated cutting tool comprising: a substrate anda coating layer formed on a surface of the substrate, the coating layerincluding in this order from the substrate side: a TiCN layer; anintermediate layer comprised of a compound of at least one kind selectedfrom the group consisting of a Ti carbonate, a Ti oxynitride and a Ticarboxynitride; and at least one α-type aluminum oxide layer, wherein,in the α-type aluminum oxide layer, a texture coefficient TC (1,2,11) ofa (1,2,11) plane represented by formula (1) below is 1.4 or more, anaverage thickness of the α-type aluminum oxide layer is from 1.0 μm ormore to 15.0 μm or less, and a residual stress value in a (1,1,6) planeof the α-type aluminum oxide layer is, in at least part thereof, from−300 MPa or higher to 300 MPa or lower, $\begin{matrix}{{{TC}\left( {1,2,11} \right)} = {\frac{I\left( {1,2,11} \right)}{I_{0}\left( {1,2,11} \right)}\left\{ {\frac{1}{8}{\sum\frac{I\left( {h,k,l} \right)}{I_{0}\left( {h,k,l} \right)}}} \right\}^{- 1}}} & (1)\end{matrix}$ (In formula (1), I (h,k,l) denotes a peak intensity for an(h,k,l) plane in X-ray diffraction of the α-type aluminum oxide layer,I₀ (h,k,l) denotes a standard diffraction intensity for an (h,k,l) planewhich is indicated on a JCPDS Card No. 10-0173 for α-type aluminumoxide, and (h,k,l) refers to eight crystal planes of (0,1,2), (1,0,4),(1,1,0), (1,1,3), (0,2,4), (1,1,6), (2,1,4) and (1,2,11).
 2. The coatedcutting tool according to claim 1, wherein, in the α-type aluminum oxidelayer, the texture coefficient TC (1,2,11) is from 2.0 or more to 6.9 orless.
 3. The coated cutting tool according to claim 1, wherein a ratioI₃₁₁/I₂₂₀ of a peak intensity I₃₁₁ for a (3,1,1) plane in X-raydiffraction of the TiCN layer to a peak intensity I₂₂₀ for a (2,2,0)plane in X-ray diffraction of the TiCN layer is from 1.5 or more to 20.0or less.
 4. The coated cutting tool according to claim 3, wherein anaverage thickness of the TiCN layer is from 2.0 μm or more to 20.0 μm orless.
 5. The coated cutting tool according to claim 1, wherein anaverage thickness of the coating layer is from 3.0 μm or more to 30.0 μmor less.
 6. The coated cutting tool according to claim 1, wherein thecoating layer comprises a TiN layer as an outermost layer on a sideopposite to the substrate.
 7. The coated cutting tool according to claim1, wherein the substrate is comprised of any of a cemented carbide,cermet, ceramics and a sintered body containing cubic boron nitride. 8.The coated cutting tool according to claim 2, wherein a ratio I₃₁₁/I₂₂₀of a peak intensity I₃₁₁ for a (3,1,1) plane in X-ray diffraction of theTiCN layer to a peak intensity I₂₂₀ for a (2,2,0) plane in X-raydiffraction of the TiCN layer is from 1.5 or more to 20.0 or less. 9.The coated cutting tool according to claim 2, wherein an averagethickness of the coating layer is from 3.0 μm or more to 30.0 μm orless.